Abstract of the day #2: The frequency and significance of the word length effect in neglect dyslexia

Neglect patients often omit or misread initial letters of single words, a phenomenon termed neglect dyslexia. Omissions of whole words on the contralesional side of the page during paragraph reading are generally considered as egocentric or space-based errors, whereas misreading of the left part of a word can be viewed as a type of stimulus-centred or word-based, neglect-related error. The research of the last decades shed light on several effects of word features (such as written word frequency, grammatical class or concreteness) that modulate the severity of neglect dyslexia. Nevertheless, almost all studies about those modulating factors were case studies and some of them have not been replicated yet. Therefore, to date we do not know how relevant such effects of different word stimuli are for a population of neglect dyslexia patients. Knowing their incidence would improve our theoretical understanding of neglect dyslexia and promote the development of standardized neglect dyslexia assessments, which are lacking so far. In particular, case studies have shown that neglect dyslexia error frequency increases systematically with word length (word length effect, WLE) while other single case studies found contrary results. Hence, the existence of the WLE in neglect dyslexia is unsettled and its incidence and significance in stroke patients is unknown. To clarify this issue we evaluated the relation between word length and the extent (number) of neglected or substituted letters within single words in neglect dyslexia (neglect dyslexia extent, NDE) in a group of 19 consecutive neglect dyslexia patients with right hemisphere lesions. We found a clear WLE in 79% (15 of 19) of our neglect dyslexia patients, as indicated by significant correlations between word length and NDE. Concurrent visual field defects had no effect on the WLE in our sample, thus showing no influence of early visual cortical processing stages on the WLE in neglect dyslexia. In conclusion, our results suggest a clear relationship between word length and reading errors in neglect dyslexia and show that the WLE is a frequent phenomenon in neglect dyslexia.